Sandal With Pressure-Adjustable Air Cushion

ABSTRACT

A sandal with a pressure-adjustable air cushion includes a platform with a recess formed therein for receipt of a cushion. The cushion has a foot-engaging pad attached to a bladder. The pad is made of a thicker, somewhat less flexible material than the bladder which is made of a highly flexible material but strong enough to withstand the pressure applied by the feet of an individual wearing the sandal. The pad rides on top of the bladder and is adhered to the platform to hold bladder in place in the recess. The gas in the cushion can be evacuated or replenished through a valve in its side, ideally near the instep, by using a small valve and pressurized canister preferably containing carbon dioxide or other suitable gases.

SUMMARY OF THE INVENTION

Briefly recited and according to its major aspects, the present invention is a sandal with a pressure-adjustable air cushion. The sandal includes a platform and foot securement. The platform has a recess formed in it that extends close to but within the periphery of the platform for receipt of the air cushion and holds the cushion in place. The cushion includes a foot-engaging pad made of a suitable material and made in a thickness that naturally tends to maintain its contour without undue rigidity. The pad covers a bladder and holds it in the recess. The bladder is made of a thin material that is highly flexible but strong enough to withstand an internal pressure of a gas and the external pressure applied by the foot of a wearer when standing and walking while wearing the sandal. The gas in the cushion may be evacuated or replenished through a valve in the side of the bladder, ideally proximate to the instep, using a small pressurized canister of gas.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 is a perspective view of a sandal according to the present invention; and

FIG. 2 is a perspective, exploded view of the sandal of FIG. 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

Referring now to the FIGS. 1 and 2, there is illustrated in perspective in both an assembled and exploded view, respectively, a sandal 10 according to an embodiment of the present invention. Sandal 10 includes a platform 12 that may be in the shape of a foot. Platform 12 may be in the shape of an abstract foot, that is, wider toward one end and narrower toward the opposite end, or roughly in a shape identifiable as a foot, or formed to be slightly larger than a particular shoe size.

Platform 12 is formed with a recess 14 (FIG. 1) that is at least slightly larger than a foot and may be in the shape of a foot and in a particular foot size or somewhat oversized. A foot securement 16 is attached to platform 12. Foot securement 16 is a structure that helps the wearer to hold sandal 10 to his or her foot. Foot securement 16 as shown is a simple strap extending over the metatarsal area of the wearer's foot, but other foot securements are possible, too. For example, on common sandals known as “flip-flops”, foot securement 16 is a three-point strap with ends attached to platform 12 on either side of the wearer's foot and a third end attached to platform 12 between the big toe and the next-to-big toe of the wearer's foot. Other foot securements 16 may include additional straps, perhaps buckles, including a strap that passes behind the wearer's heel. The present invention may apply to any type of foot securement 16.

Platform 12 may be made of any durable, somewhat flexible material but is preferably made of a natural or synthetic, rubbery composite material with good traction and provides protection for the wearer's foot sole from sharp objects underfoot. A natural or synthetic rubber or plastic would be suitable material for platform 12.

A cushion 18 is carried in recess 14. Cushion 18 is dimensioned to fit snuggly into recess 14, to be coextensive with recess 14 so as to not shift when in place, and may be adhered to platform 12.

Cushion 18 includes a pad 20 and a bladder 22. Pad 20, which provides a foot-engaging surface rides on top of bladder 22 and is made of a thicker and stiffer material than that of bladder 22, roughly 6 mm (¼ inch). Bladder 22 is made of a thin, somewhat elastic material such as a natural or synthetic rubber or plastic that can contain a volume of gas under pressure from within and withstand a non-uniform loading by the foot of the wearer of sandal 10 who may be walking. Pad 20 provides a foot engaging surface for the wearer, and preferably has a soft surface, which may be textured, a surface that can be cleaned and may be made of a manmade or natural material. Pad 20 also helps to hold bladder 22 in place in recess 14 and is attached, preferably by adhesives, to platform 12.

Pad 20 and bladder 22 cooperate with and compensate for each other to provide a suitably stable surface for the wearer of sandal 10 that adjusts, cushion-like, to the varying of the pressure distribution from the weight of a walking wearer, as transmitted through and distributed by the foot of the wearer. Bladder 22 responds to pressure changes from the movement of the wearer by redistributing its internal gas volume away from the high pressure areas of the heel and ball of the foot and thereby provide more support to adjacent areas of the foot for greater comfort. Pad 20 not only preserves the lateral dimensions of cushion 18 to provide a more stable surface over a wide range of bladder pressures, particularly at higher inflation pressures, but also helps to spread the pressure of the wearer's foot over a wider area.

Cushion 18 has a port 24 on one side, accessible through a port 25 in platform 12 and approximately mid-foot so that it is close to the instep area of the wearer's foot, where it is not likely to interact with the wearer's foot and present an irritation. Port 24 is used to admit gas into and out of bladder 22 and is normally closed to prevent gas escape but can be opened by a valve 28 to allow excess gas to escape or to permit additional gas to be added from a canister 26 for a firmer sole.

Also part of the present embodiment is a gas canister 26 containing a quantity of gas under pressure. Valve 28 is threaded to canister 26 and can be used to augment the amount of gas in bladder 22 to provide a thicker, firmer cushion 18 or reduced to provide a softer but relatively thinner cushion. Valve 28 is inserted into port 24 and regulates the amount of gas added or subtracted from bladder 22. Preferably the gas is carbon dioxide but air or other gases can be used. Molecules of carbon dioxide are larger than the majority of air molecules, principally diatomic oxygen and nitrogen that tend to escape more easily.

Canister 26 and valve 28 are designed so that canister 26 can supply gas at sufficient pressure to inflate bladder 22 to provide full cushioning for a large person and pad, even when bladder is fully inflated does not depart substantially from a flat shape. Pad may bow slightly but not to the extent it creates a noticeably rounded surface for the wearer's foot. Canister 26 and valve designed to regulate gas pressure in bladder and to avoid over-pressurization.

Bladder 22 may also be provided with internal structure, anchors (not shown), to prevent it from ballooning when inflated to higher pressures but to not interfere with it flattening when fully deflated. Anchors are straps connect the top and bottom walls of bladder 22 and are not resilient so that, upon increasing the gas volume on the interior of bladder 22, and once they are fully extended, they then limit the extend of the vertical expansion of cushion 18 by fixing the separation of the top and bottom of bladder 22, whereby the overall expansion is then driven laterally.

Gas is added through port 24 using valve 28 and canister 26 so that sandal 10 responds better to the greater pressure of a particular wearer's foot on cushion 18 and can be vented through port 26 for lighter wearers.

Those skilled in sandal design will understand that many modifications and substitutions may be made in the foregoing description of embodiments without departing from the spirit and scope of the present invention. 

What is claimed is:
 1. A sandal, comprising: (a) a platform encompassing the shape of a foot, said platform having a recess formed therein; (b) foot securement attached to said platform; (c) a cushion dimensioned to be received within said recess; (d) a valve carded by said cushion; and (e) a canister containing compressed gas for inflating said cushion thought said port valve.
 2. The sandal as recited in claim 1, wherein said cushion further comprises a foot-engaging pad attached to a bladder, said port being in fluid communication with the interior of said bladder.
 3. The sandal as recited in claim 2, wherein said bladder contains anchors to to retard ballooning and provide the user with a reasonably flat and stable feeling surface on which to walk and stand
 4. The sandal as recited in claim 2, wherein said foot-engaging pad has maintain lateral dimensions over a useful range of inflation pressures.
 5. The sandal as recited in claim 1, wherein said port is carried by said cushion proximate to the instep portion of said cushion.
 6. The sandal as recited in claim 1, wherein said canister contains carbon dioxide or air or other suitable gas. 